Erasable-programmable-read-only-memory (hereinafter called EPROM) packages that can be erased by an ultra-violet (UV) light ray consist of an EPROM chip directly mounted on a printed circuit board having conductive interconnection patterns formed on the main surface of the board, or on a lead frame. Referring to FIG. 1, an example of a prior art plastic package, a printed circuit board 10 made of an insulating material, such as glass-filled epoxy resin, has a chip mounting portion 12 and conductive interconnection patterns 13 on a main surface thereof. The chip mounting portion 12 is one portion of the conductive interconnection patterns 13. One end of each of the patterns 13 is adjacent to the chip mounting portion 12 and another end of the patterns connects to individual terminals (not shown). An EPROM chip 14 is mounted on the chip mounting portion 12 by, for example, a conductive adhesive 15, in such a manner that the active surface 4 thereof faces upward. Each of the pad electrodes of the EPROM chip 14 may be connected to one end of each of the patterns 13 with thin metal wires 16. One of the pad electrodes of the EPROM chip 14 connects to the chip mounting portion 12 with a thin metal wire so as to make an ohmic contact with the substrate of the chip 14. Then, the combined portion comprising the thin metal wires 16, the EPROM chip 14, and portions of the conductive patterns 13 are encapsulated by a cap or cover 17. The cap 17 is typically made from an UV opaque material, such as ceramic or black plastic, and contains a window 19 capable of transmitting UV light. The cap 17 is securely fixed to the board 10 with an adhesive 18 such as epoxy. In order to prevent the EPROM 14 from becoming accidentally erased, an opaque, light tight covering 5 is typically placed over the window 19. The covering 5 takes many forms, such as permanent coatings, temporary coatings, adhesive tape dots, removable plugs, removable caps, additional housings for the package, or conformal coatings. Each of these requires that the covering 5 be physically removed whenever the user desires to erase the information contained in the EPROM 14, and then replaced or reassembled prior to reprogramming the EPROM.
Another example of an EPROM package, a dual-in-line package (hereinafter simply called a DIP package), is illustrated in FIG. 2. The EPROM package includes an EPROM chip 24, a lead frame 21, leads 23, and a cap, cover, or housing 27 formed from alumina ceramic (Al.sub.2 O.sub.3) or plastic resin. The EPROM chip 24 is bonded or mounted on a chip mounting portion 22 of the lead frame 21, and contains electrode pads which are connected to the lead frame with thin metal wires 26, such as gold or aluminum. A window 29 through which UV light may pass to the EPROM chip 24 is contained in the center of the cap 27. In order to prevent the EPROM 24 from becoming accidentally erased, an opaque, light tight covering 25 is typically placed over the window 29. The covering 25 takes many forms, as described above. The covering 25 must be physically removed whenever the user desires to erase the information contained in the EPROM, and then replaced on the DIP prior to reprogramming the chip.
DIP packages and other conventional EPROM packages suffer from the disadvantage of having to continually remove the window covering 25 when erasing the programmed information, and then replacing the covering 25 to prevent accidental erasure of the chip by stray light. It would be a significant advantage if one were able to erase the chip without having to physically remove the covering 25 and replace it each time.